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An Investigation of Contamination Risk

at Greenside Lead Mine, Cumbria.

Ghosh, A.

This thesis is submitted in part fulfilment of the

requirements for the B.Sc. degree in EnvironmentalScience at the University of Lancaster.

January 2001

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ABSTRACT

In 1999 the Lake District National Park Authority commissioned Scott Doherty

Associates (SDA) to undertake a geo-environmental and structural engineering

assessment of the site of the disused Greenside Lead Mine and Kepple Cove Dam.

The Environment Agency conducted their own risk assessment of the site in the same

year. The principal risk was identified to be a further failure of the tailings dam to the

west of Swart Beck and the resultant lead contamination of the surrounding water

system. Whilst this report considers the range of risks that are posed by the site, it

focuses on the risk of lead contamination, particularly from the two tailings dams. A

review of the SDA (2000) report was carried out and the use of risk assessment

models such as RISC-Human appraised. In an effort to enhance the assessment of

risk from the mine, Atomic Absorption Spectrometry was used to determine the lead

content of grass samples obtained from the tailings dams. The subsequent data were

included in an ingestion calculation to determine whether there is a risk of

contamination to sheep that graze on the tailings dams. Such a risk was found to be

high and a recommendation made to prohibit grazing on the site. In addition, the lead

content of soil samples obtained from both tailings dams was determined by X-ray

Fluorescence Spectrometry. Elevated levels of lead were found in all the samples.

However, no correlation was found to exist between lead content and (i) depth of the

soil from the surface, (ii) pH, (iii) organic matter content or (iv) percentage of

particles

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CONTENTS

Page

Nos.

Acronyms and Abbreviations i

List of Figures ii

List of Tables iv

Section 1.0 INTRODUCTION 1

1.1 Location 1

1.2 Topography 4

1.3 Geology 5

1.4 Greenside Mining History 6

1.5 Summary of the Legacy of Past Mining Activities 8

1.6 Dissertation Aims 12

Section 2.0 PROPERTIES AND BEHAVIOUR OF LEAD 13

2.1 Bioavailability of Lead 14

2.2 Toxicity and the Human Food Chain 15

2.3 Legislation and Lead Standards 16

Section 3.0 RISK ASSESSMENT PROCEDURES AND APPLICATION 17

3.1 Definition 17

3.2 Risk Assessment Procedures 18

3.3 Land Exposure Computer Models 19

3.3.1 Probabilistic Models 19

3.3.2 Deterministic Models 19

3.3.3 Fugacity Models 203.4 The Application of Risk Assessments to Disused Mining

Sites

20

3.5 Review of the SDA (2000) Assessment of the Greenside

Mine Site

21

3.5.1 Introduction 21

3.5.2 Human Health Assessment 22

3.5.3 Assessment Standards 22

3.5.4 Principal Findings and Recommendations 23

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Section 4.0 EXPERIMENTAL METHODS 24

4.1 Sample Collection and Storage 24

4.2 Sub-sampling Procedure 29

4.3 Laboratory Water 30

4.4 Glassware 30

4.5 Sample Handling 30

4.6 Lead Content in Grass 31

4.7 Sheep Ingestion Calculation 31

4.8 Lead Content in Soil 32

4.9 Organic Matter in Soil 33

4.10 Soil pH 33

4.11 Grain Size Analysis 34

Section 5.0 EXPERIMENTAL FINDINGS 35

5.1 Grass Samples 35

5.2 Sheep Grazing 38

5.3 Soil Samples 39

5.3.1 Lead Content by XRF 39

5.3.2 Soil pH, Organic Matter and Grain Size Analysis 41

Section 6.0 DISCUSSION 44

6.1 General Risks 44

6.2 The Tailings Dams 45

6.2.1 Geotechnical Stability 45

6.2.2 Physical Characteristics 45

6.2.3 Lead Content 46

6.2.4 Risk Probability Analysis 47

6.2.5 Factors Influencing Lead Bioavailability 49

6.2.6 Groundwater Contamination 50

6.3 Contamination Risk to Sheep 50

6.3.1 Lead Content of Grass Samples 50

6.3.2 Lead Ingestion Calculation 52

6.4 Surface Water Contamination 53

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6.5 Sediment Contamination 53

6.6 Water Quality 54

6.7 Instability Risk from Mine Entries and Underground

Workings

55

6.8 Experimental Uncertainty and Errors 55

Section 7.0 SUMMARY AND CONCLUSIONS 57

REFERENCES 62

Appendix A: The Creation of the Tailings Dams 65

Appendix B: Grass Sample Analysis Procedure and Data 67

Appendix C: Sheep Grazing: Ingestion Calculation 71

Appendix D: Soil Sample Analysis Procedure and Data 74

Appendix E: Method and Data for Organic Matter Analysis 78

Appendix F: Method and Data for Soil pH Analysis 80

Appendix G: Grain Size Analysis 82

ACKNOWLEDGEMENTS 94

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ACRONYMS AND ABBREVIATIONS

AAS Atomic Absorption Spectrometry

CLEA Contaminated Land Exposure Assessment model

EA Environment Agency

EC European Commission

ECR European Commission Regulation (lll/5125/95 Rev.3)

EQS Environmental Quality Standard

GLC Greater London Council Guidelines

ICRCL Interdepartmental Committee on the Redevelopment of Contaminated Land

IMS Industrial Methylated Spirits

LHLM Low Horse Level Mine

LDNP Lake District National Park

pers. comm. Personal communication

QCA Quality Control Actual

QCD Quality Control Difference

QCE Quality Control Expected

RISC-Human Risk Identification of Soil Contamination - Human

SDA Scott Doherty Associates

SSSI Site of Special Scientific Interest

TD1 Tailings Dam 1

TD2 Tailings Dam 2

UK United Kingdom

WA Walldel Armstrong

XRF X-Ray Fluorescence Spectrometry

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List of Figures

Description Page Nos.

Figure 1: An Ordnance Survey map (1:10,000 scale) indicating the

mine site boundaries.

2

Figure 2: A sketch map indicating the various mine workings at the

site (Tyler, 1998).

6

Figure 3: Photo of the converted mill buildings and Swart Beck taken

at NGR NY 365174 looking North North East.

8

Figure 4: Photo of collapsed underground workings at Gilgowars

Level taken at NGR NY 359185 looking North North West.

9

Figure 5: Photo of a leat which lies above TD2, taken at NGR

NY364175 looking South.

10

Figure 6: Photo of a leat running between TD1 and the scree slope

behind it. The photo has been taken at NGR NY 366176

looking West.

11

Figure 7: A sketch map of the site to indicate the location of all the

sampling sites.

25

Figure 8: A photo of the control site taken at NGR NY 363173

looking South.

26

Figure 9: A photo of pit D taken at NGR NY 366175. 27

Figure 10: A photo of pit G taken at NGR NY 364175. 27

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Figure 11: A soil and grass sample chart to indicate the depth from the

surface in cm at which the samples were taken and a brief

description of each.

28

Figure 12: A calibration curve of absorbance against lead concentration. 36

Figure 13: A graph to indicate the range of lead contaminant body

burden on a sheep grazing from 0 to 365 days a year on

either the control site, TD1 or TD2. Lead content limits for

sheep and lamb cuts are displayed.

38

Figure 14: A graph to show the cumulative mass percent for each soil

sample.

43

Figure 15: Three graphs containing data obtained from (A) pit A, (B)

pit D and (C) pit G. The lead content of the soil samples is

displayed together with the organic matter content, the pH

value and the percentage of the sample that contains

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List of Tables

Description Page Nos.

Table 1: A summary of maximum lead content levels applicable to

factors under consideration in this investigation.

16

Table 2: Absorbency readings and standard deviations for the

standard lead calibration solutions.

35

Table 3: Content of lead in mg/kg of dry weight grass for each grass

sample and blank.

37

Table 4: XRF derived lead content values in mg/kg of soil samples

from the control site, TD1 and TD2.

40

Table 5: Lead content, pH, percentages of organic matter and grain

size

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Table 11: The contaminant body burden on a sheep from contaminant

ingestion depending on how many days in a year it grazes on

either the control site, TD1 or TD2.

72

Table 12: Geological minors content of control site soil samples as

determined by XRF Analysis.

75

Table 13: Geological minors content of TD1 soil samples as

determined by XRF Analysis.

76

Table 14: Geological minors content of TD2 soil samples as

determined by XRF Analysis.

77

Table 15: Organic Matter Content of Soil Samples. 79

Table 16: pH readings obtained for soil samples. 81

Table 17: Mass of beaker and soil sample relating to

procedure followed for grain size analysis.

85

Table 18: Dry Mass of Sediment Fractions. 86

Table 19: Grain Size Distribution of Soil Samples. 87

Table 20: Cumulative mass finer (%) and spherical diameter ( in m)

for soil samples.

93

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1.0 INTRODUCTION

In 1999 the Lake District National Park Authority commissioned Scott Doherty

Associates (SDA) to undertake a geo-environmental and structural engineering

assessment of the site of the disused Greenside Mine and Kepple Cove Dam. The

Environment Agency (EA) conducted their own risk assessment of the site in the

same year. Both reports determined the principal risk to be a further failure of the

tailings dam to the west of Swart Beck and the resultant lead contamination of the

surrounding water system.

Whilst elements of a risk assessment were carried out by SDA (2000), certain

elements were not considered. It is the latter that this dissertation focuses on in an

attempt to enhance the assessment of risk from the mine site. Consequently, the lead

content of the tailings dams and the contamination risk posed to sheep grazing on the

site have both been investigated. This dissertation has been carried out in conjunction

with other Lancaster University Students who focused on the impact of the mine on

the surrounding water system and sediments. Their findings are referred to within this

report.

1.1 Location

Greenside Lead Mine (National Grid Reference NGR NY 365174) is situated to the

west of the Glenridding screes and approximately 1.5km to the west of Glenridding

village within the Lake District National Park (LDNP). The LDNP Authority is

responsible for the management and upkeep of the site having obtained ownership of

it in 1965. The extent of the site is indicated in Figure 1.

As can be seen from Figure 1, Swart Beck flows through the site before feeding into

Glenridding Beck. The latter flows adjacent and to the south of the site before

entering Lake Ullswater.

The majority of the site, including Keppel Cove Dam, is contained within the

Helvellyn and Fairfield Site of Special Scientific Interest (SSSI). However the

tailings dams and the adjacent mineral processing areas including the Low Horse

Level Mine (LHLM) are not included in this designation. The mine site, excluding

Tailings Dam 1 (TD1), is a Scheduled Ancient Monument. (SDA, 2000).

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Figure 1: An Ordnance Survey map (1:10,000 scale) indicating the site boundaries. Reproduced from Ordnance Survey maps by permission of

Ordnance Survey on behalf of The Controller of Her Majestys Stationery Office, Crown Copyright NC/01/021.

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1.2 Topography

Greenside Lead Mine is situated within an area of varied topography that includes the

steep, sparsely vegetated Glenridding screes to the east as well as more gentle slopes

leading to Sheffield Pike.

There is a single road access to the site from Glenridding village to the east. The road

forks just to the west of the site into two bridlepaths. One leads to the north of the site

and the early mining workings before heading west to the village of Legburthwaite

(Sticks Pass). The other bridlepath follows Glenridding Beck to the west before passing

to the north of Red Screes and merging with several other bridlepaths.

The impact of Greenside Lead Mine is clearly visible in what could otherwise be

described as an unspoilt area. Due to the extensive impact of past mining activity, the

topography of the site is very much man-made particularly with respect to TD1 and

Tailings Dam 2 (TD2).

At the top of the site there is evidence of early mining activities in the form of extensive

spoil heaps in a level area formed by glacial erosion and on which also exists numerous

mounds of glacial moraine.

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1.3 Geology

The Greenside site is underlain by a vast granite intrusion and a layer of sedimentary

rocks known as the Skiddaw Slates. These are overlain with a hard, fine-grained rock

known as the Borrowdale Volcanics which Murphy (1996) states, originated from

volcanic ashes and lavas that over time were buried and subjected to high levels of

pressure and temperature. The rock is predominately of andesitic composition and

contains an intrusive dyke composed of quartz porphyry.

The site contains a large amount of surface deposits that are both naturally occurring (e.g.

glacial till and screes) and anthropogenic (e.g. spoil tips and tailings dams) (Murphy,

1996).

The Greenside Vein strikes almost due north-south. Murphy (1996) estimates that it has

a downthrow to the east of about 15-30m although the horizontal slip on the strike is less

than 3m. The dip of the vein is to the east at an angle of about 70 degrees to the

horizontal but this varies very substantially from place to place. The vein is likely to

have been created from the gradual deposition of minerals dissolved in water percolating

into the fissure. The fissure would have been as a result of geological activity in the area

that involved large crustal movements to cause the rocks to fold and fracture.

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1.4 Greenside Mining History

It is a matter of contention as to when mining activity on the Greenside site commenced

with suggested dates varying between 1692 and 1750. What holds no such contention is

the fact that Greenside was Cumbrias richest and deepest lead mine. Within its

operational lifespan, it was mined largely uninterrupted for a 150 year period. In 1962,

mining activities at Greenside ceased after it was decided that all economically

recoverable ore had been abstracted from the site (Murphy, 1996; Tyler, 1998).

Initially the mine was a modest operation but its expansion over the years was reflected

in the growth of the local population. What was a group of a few farms and homesteads

in the area of Glenridding and Patterdale, grew into significant populations with thearrival of miners and their families.

Murphy (1996) describes how in 1825, the Greenside Mining Company was officially

formed by a group of local businessmen. A lease to carry out mining activities was

obtained from the two landowners of the day, Henry Howard and William Marshall.

Although ownership of the mine inevitably changed during its long history, a common

desire to fulfil the mines full potential encouraged successive owners to adopt new

innovative technology of the day.

In 1891 Greenside was the first mine in Britain to install electrical winding gear at the

shaft top. In 1893 the mine achieved another first by installing an electric locomotive to

run along Lucy Tongue Level, transporting ore to the mill. The electricity was generated

by water from Kepple Cove Tarn which drove turbines coupled to 600 volt dynamos

(Adams, 1995).

The earliest workings are located on some of the highest elevations of the site with new

workings focusing on lower levels, as the mine got deeper. Figure 2 is a sketch map

indicating the various mine workings at the site. The Lucy Tongue Level was the lowest

level to be driven, with work commencing in 1853 and finishing in 1869 (Murphy,

1996). According to Adams (1995), by the time the mine finally closed in 1962, the

deepest workings were 1,420 feet (432m) below the Lucy Tongue Level and 3,000 feet

(912m) below the top of the hill.

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Figure 2:A sketch map indicating the various mine workings at the site (Tyler, 1998).

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Due to the high silver content of the ore, lead as well as silver was extracted and sold

throughout the mines history; significantly assisting in its financial success. Murphy

(1996) states that nearly all the silver extracted from Greenside was made into coins by

the Royal Mint in London. It has been estimated by Adams (1995) that the Greenside

vein yielded a total of approximately 2,400,000 tons (2 x 106

Mg) of ore and 2,000,000

ozs (6 x 104kg) of silver.

The extraction of lead and silver from the Greenside vein was interrupted on a few

occasions by financial crises that resulted in the company of the time going out of

business or into liquidation.

In the late 1920s, in conjunction with a fall in the price of lead, large compensationclaims were paid out following the Kepple Cover Dam burst in 1927 when the village of

Glenridding was flooded. These two factors forced the mine company of the time out of

business and brought about the suspension of mining activity until a new owner could be

found (Murphy, 1996; Tyler, 1998).

In the early 1940s, it became clear that the Greenside vein would not be able to be

economically exploited for much longer. An underground and surface exploration

programme carried out in 1947 failed to locate much needed new deposits. Prior to the

mines final abandonment in 1962, underground seismic tests were carried out by the

Atomic Energy Authority (Adams, 1995; Murphy, 1996; Tyler, 1998).

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1.5 Summary of the Legacy of Past Mining Activities

Today, the site is disused in relation to mining activities with the remaining, intact

mining buildings having been converted into private hostels. These buildings are clearly

visible in the foreground of Figure 3.

Figure 3: Photo of the converted mill buildings and Swart Beck taken at NGR NY

365174 looking North North East.

The local area is popular with tourists and walkers although access to areas of Swart

Beck together with the tailings dams, Swart Beck dressing floors and the mine adits are

fenced off and public access denied for health and safety reasons.

Paths used by the miners when the mine was in operation are clearly visible. Other

visible man-made impacts include the spoil heaps, tailings dams and leats. Massive

collapses have occurred of the higher underground workings and Figure 4 shows the

collapse at Gilgowars Level.

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Figure 4: Photo of collapsed underground workings at Gilgowars Level taken at NGR

NY 359185 looking North North West.

Further visual impacts have arisen from revegetation schemes designed to increase slope

stability and reduce slope erosion of the tailings dams. The most recent (1965) being the

turfing of TD1 and TD2, together with the planting of conifers at the foot of the former.

The system of leats that were built on the site is still largely visible. Only the leat that is

positioned above TD2 has had any significant maintenance carried out on it since the

mines closure in 1962 (Guy Weller, LDNP Authority, pers. comm., 2000). Figure 5

shows a leat which lies above TD2 and is clearly in some need of repair.

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Figure 5: Photo of a leat which lies above TD2, taken at NGR NY 364175 looking

South.

Figure 6 shows the leat running between TD1 and the scree slope. This leat is in a good

condition and enables surface water draining from the scree slope above TD1 to be

diverted to the side of it. This consequently reduces infiltration and related slope

instability.

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Figure 6: Photo of a leat running between TD1 and the scree slope behind it. The photo

has been taken at NGR NY 366176 looking West.

The remains of sections of track and buffers, provide evidence of the tramway system

that was implemented at the site for the removal of ore and waste from the mine

workings.

However, the most major and visible legacy of the mine has been the creation of a

number of spoil heaps and tailings dams. Appendix A provides information about the

creation of the two tailings dams.

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1.6 Dissertation Aims

A full risk assessment of the Greenside Lead Mine site is too ambitious a task to

encompass in this report given the size of the site, the range of expertise required and the

constraints on both time and finances. Instead, whilst this report will identify the range

of risks that the site poses, it will primarily focus on the issue of lead contamination. The

risk that lead contamination poses to animals grazing on the site, local water systems and

sediment as a direct result of past mining activities will be considered. Findings will be

placed within the context of current legislation.

A review of the SDA (2000) report will enable conclusions to be drawn as to whether all

the risks related to the site were considered and effectively assessed by them. Thesuitability and limitations of risk assessment models such as the RISC-Human model

which was adopted in the SDA (2000) assessment, will be appraised.

Herbage tests will be carried out on both major tailings dams and a control site.

Preliminary conclusions as to whether it is advisable for sheep to graze on the site given

their direct exposure to potentially lead contaminated grass will be drawn from the results

of these tests. Evidence of water and sediment contamination will be sought from data

compiled by a variety of sources including SDA, the EA and other Lancaster University

dissertation students.

Finally, recommendations will be made as to how the risks posed by contamination and

other factors should be addressed.

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2.0 PROPERTIES AND BEHAVIOUR OF LEAD

Lead is a naturally occurring metal that can be found in a variety of forms such as lead

sulphide (PbS), otherwise known as galena. Anthropogenic sources of lead include

activities such as lead mining and smelting both of which took place at the Greenside site

for several hundred years before the mines closure in 1962.

Thornton (1980) estimates that approximately 4000km2 of land in the United Kingdom is

contaminated with lead largely as a result of past mining and smelting related activities.

According to Radojevi (1999) soils in the vicinity of mines and smelters have been

found to have lead concentrations >10,000mg/kg.

Salomons et al. (1995) state that excessive lead levels in the environment can have an

impact on a number of factors as listed below. Work has been carried out on the first

three of these to assess the risk that lead from the mine site poses to them.

i) Human health (through the consumption of contaminated water or accidental

ingestion of the soil).

ii) Pasture (free grazing access is given to sheep. Ingestion of lead by the sheep may

pose a threat to the food chain if the animals or their young are bred for

consumption).

iii) Surface and ground water quality (seepage of water through the mine workings and

tailings dams into the water systems).

iv) Natural ecosystem (soil degradation, native flora and fauna).

v) Agriculture.

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2.1 The Bioavailability of Lead

A number of factors are thought to influence the bioavailability of lead in soils and its

capacity to retain lead. It was these factors that helped determine the type of analysis

carried out on the soil and grass samples collected from the mine site. Possible

influencing factors include:

1. Particle size

Clay sized ions of lead (

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Different species of plant have been found by Sieghardt (1990) to vary in their ability to

uptake lead from the soil. It has also been established that different parts of the plant

accumulate lead in different concentrations. The plant roots are usually found to contain

the highest concentrations.

2.2 Toxicity and the Human Food Chain

Lead is not essential to plants or animals and can prove to be toxic to both if taken up in

certain forms and at high enough concentrations. Alloway (1995) states that the normal

range of lead concentration in plants is 0.2-20mg/kg with toxicity being likely when

concentrations are above 30-300mg/kg. Some plants are able to accumulate lead at a

level that although harmless to the plant itself, can be harmful to animals and humans if

ingested by them. This situation poses a risk to the human food chain particularly if

animals destined for human consumption, graze on the contaminated plants.

It was with the risk to the human food chain in mind that herbage tests were carried out

on the tailings dams at the Greenside site. The findings were incorporated into an

ingestion calculation to determine whether a risk of contamination was posed to sheep

grazing on the site and in turn to the human food chain through the consumption of lamb.

According to Radojevi (1999) the ingestion of foods of plant and animal origin is the

primary route by which heavy metals impact on human health. Drinking water and

inhalation of airborne particles have generally been found to make a smaller contribution

to the total intake of toxic metals.

Lead poisoning and detrimental effects relating to exposure of lead can cause a numberof health problems in humans and particularly in children. Salomons et al. (1995) state

that in the latter, these can include nervous system disorders, hyperactivity and learning

difficulties.

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2.3 Legislation and Lead Standards

Over time there has been an increased awareness of the health risks posed by elevated

levels of lead. Measures have been taken to reduce its introduction into the environment

from anthropogenic sources. National and international legislation set lead limits up to

which are considered acceptable for human health, different types of food and the

environment. Table 1 below provides a summary of some of the current standards that

are applicable to the lead mine site and this investigation. Information relating to the

assessment standards that were adopted by SDA when analysing soil samples is provided

in the next section of this report.

Table 1: A summary of maximum lead content levels applicable to factors underconsideration in this investigation.

Category Lead Limits Description & Advisory Body

Drinking water 50g/L

50g/L*

10g/L

European Commission standard

UK Government standard

World Health Organisation standard

Salmonid

watercourses

2g/L Environmental Quality Standard (EA, 2000)

Food

Sheep

Lamb cuts

0.05-0.2 mg/kg

0.03 mg/kg

Lead limit range proposed by European

Commission Regulation (lll/5125/95 Rev.3)

(Food Standards Agency, 2000).

Mean lead concentration for lamb cuts

(Food Standards Agency, 2000).

Blood Levels

Adults

Children

2.0 mol/L

1.35 mol/L

Significant exposure to lead is deemed to

have occurred if these levels are reached.

* this maximum level will be reduced to 10ppb within the next fifteen years to come in

line with the World Health Organisations standard for drinking water.

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3.0 RISK ASSESSMENT PROCEDURES AND APPLICATION

3.1 Definition

A risk assessment is an evaluation of the potential for exposure to contaminants and the

associated hazard effects (Asante-Duah, 1998). An assessment of risk can assist in the

future management of a site by the identification and quantification of its risks. The

information generated from this process enables the adoption of management strategies

which will either eliminate significant risks or reduce them to what are considered to be

acceptable levels. The strategies whilst meeting relevant legislative requirements should

also be both site specific and cost effective.

Hope (1995) proposes that an assessment of risk for a particular site will involve the

identification of:

1. the risks and the quantification of them whenever possible;

2. the risk receptors e.g. the water environment, grazing animals, human health;

3. the receptors level of exposure to a particular risk;

4. the exposure pathway (a course a chemical takes from a source to an exposed

organism);

5. the exposure routes (the way a chemical comes in contact with a receptor e.g.

ingestion);

6. the adverse effects the receptor may suffer if in contact with a particular risk;

7. preliminary suggestions as to what action could be taken to reduce or remove each

identified risk.

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3.2 Risk Assessment Procedures

There has been an increased awareness over the years of the risks posed by disused mine

sites and the associated impacts on the local environment and populations within it.

Increased scientific knowledge coupled with technological advancements has improved

the accuracy of the identification and analysis of these risks.

A variety of computer tools exist to aid the risk assessment process. All have their own

particular limitations and assumptions. It is vital that an understanding be obtained of

these two factors in order that the appropriate tool is chosen for a particular site. The

choice of an inappropriate tool may result in remediation action being taken that is not

required or vice versa.

Regardless of what tool or approach is adopted, the entire risk assessment process needs

to be transparent to ensure consistency and accountability. The Van Hall Instituut

(1999) has developed an exposure model called RISC-Human (RISC: Risk Identification

of Soil Contamination). This model allows for transparency by providing the operator

with the opportunity to include justification for any changes that are made.

Countries differ in their approach to the principal risk receptor. This difference is

reflected in the risk assessment tools developed by other countries. Default exposure and

averaging periods are likely to be appropriate to their own particular policy positions. In

the Netherlands, for example, lifetime exposure and averaging in all situations is

currently the norm and this approach is reflected in RISC-Human (EA, 2000).

The EA are currently developing a probabilistic risk assessment tool which is called

Contaminated Land Exposure Assessment model (CLEA). Documents relating to the

different factors that the EA believes should be incorporated into risk assessments are in

the process of being written and form the basis of this model (EA, 2000).

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3.3 Land Exposure Computer Models

Hope (1995) states that modelling cannot produce absolute answers regarding exposure

because of its assumptions and inherent uncertainties. However, it is a cost effective

method that can provide an initial estimate of receptor exposure to site-related

contaminants present in surface water, groundwater, sediment, soil and air media.

3.3.1 Probabilistic Models

Probabilistic or stochastic risk assessment models such as CLEA, involve the derivation

of the range of potential risks for a receptor, or the range of probably risks across a

population, from least to most at risk. This type of method does not, as Richardson

(1996) explains, eliminate the speculative nature of most risk assessments, but doesprovide the opportunity to quantify the uncertainty in the chosen model.

CLEA estimates exposure to contamination from soil and other sources, compares this to

acceptable intakes and derives a level for contamination in soil which is considered to be

acceptable for the purposes of protecting human health (EA, 2000).

3.3.2 Deterministic Models

Alternatively, deterministic risk assessment models such as RISC-Human provide a

single point estimate of an individual risk. Richardson (1996) states that this type of

model can be used to derive a worst-case risk scenario.

SDA (2000) used RISC-Human in their assessment of risk at the Greenside site. This

exposure model assesses human exposure risks that are a result of contaminated soil. It

consists of three sub-models that enable human exposure to specific media to be

estimated. The CSOIL sub-model was found to be the most relevant to the Greenside

site. It is used to derive the human toxicological intervention values for soil clean-up

standards in Holland. These intervention values are used as reference values in the

United Kingdom although RISC-Human will soon be superseded in the UK by CLEA

(Van Hall Instituut, 1999).

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The Van Hall Instituut (1999) has ensured RISC-Human provides site-specific

information by allowing the operator to change parameters from the default setting to a

value that reflects the actual site. For example, relevant soil properties such as organic

matter content can be included.

Different risk management strategies can be modelled with RISC-Human (Van Hall

Instituut, 1999). This ability allows the impact of strategy to be compared, thereby

assisting with decision-making relating to the current and future management of a

contaminated site.

3.3.3 Fugacity Models

Fate and transport models (fugacity models) predict the behaviour of contaminants basedon their physio-chemical properties e.g. solubility. Whilst other models are based on

observations of a particular substance in a particular situation (EA, 2000).

3.4 The Application of Risk Assessments to Disused Mining Sites

The implementation of the 1974 Mines & Quarries Act introduced for the first time the

idea that responsibility should be taken for disused mining sites. Although risks will

vary between different disused mining sites, common risks include:

i) stability of old workings and tailings dams/spoil heaps;

ii) the contamination of surface waters, ground waters and soil from water leaching

from old workings, tailings dams and spoil heaps;

iii) the impact that has in turn on flora, fauna and human health.

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3.5 Review of the SDA (2000) Assessment of the Greenside Mine Site

3.5.1 Introduction

In 1989 a slippage occurred in TD2, causing a large amount of tailings material to enter

Swart Beck, Glenridding Beck and Lake Ullswater. In an attempt to avoid further

unexpected slippages of this kind, the engineering company of Walldel Armstrong (WA)

were commissioned to carry out regular inspections of the site (Guy Weller, LDNP

Authority, pers. comm., 2000).

From 1989 to 1997 WA carried out visual inspections of the surface features of the site

and in particular of TD1 and TD2. However, borehole data from the tailings dams were

not obtained or analysed and consequently the potential for further slippages wentundetected (Guy Weller, LDNP Authority, pers. comm., 2000).

The inadequacy of the WA inspections was highlighted in 1997 when an unpredicted

slippage occurred in TD2 and the slippage of 1989 was further enlarged. Minor

slippages have continued to occur since 1997 in TD2 (Guy Weller, LDNP Authority,

pers. comm., 2000). The second significant failure of TD2 ensured that the need to carry

out a thorough assessment of risks from the site became a priority for the LDNP

Authority. Consequently, SDA were commissioned in 1999 to undertake a geo-

environmental and structural engineering assessment of Greenside Mine and Keppel

Cove Dam (SDA, 2000).

Whilst elements of a risk assessment were carried out by SDA (2000), not all elements

were found upon a review of their report, to have been considered. A recommendation

was made by them to restrict sheep grazing on the site. This advice was based on the

lead content of surface soil on the site rather than herbage lead content. This

investigation has redressed this omission from the assessment of risk at the site. The

lead contamination of sediments though not included in the SDA (2000) assessment has

been investigated by Kember (2000). Her findings are referred to in section 6 of this

report.

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3.5.2 Human Health Assessment

A human health risk assessment of the Greenside site was carried out by SDA (2000)

using the RISC-Human model. Data derived from the tailings dams together with that

from the Lucy Tongue Level Mine, Upper Swart Beck Dressing Floor and Lower Horse

Level Mine workings were used.

RISC-Human determined that the main exposure pathways for humans to contaminants

from all the above locations were via soil ingestion and soil inhalation. However,

according to the models findings, none of the areas posed a risk to human health.

Consequently no remedial action relating to human health from soil ingestion or

inhalation was proposed by SDA (2000). The adoption of the CLEA model for this

particular assessment would have provided more information regarding the associateduncertainty and unreliability of the models findings.

Due to the complex nature of this site, the RISC-Human model would not have been able

to replicate the exact spatial and temporal variation of its contaminant concentrations.

Inevitably assumptions and simplifications would have been made by SDA (2000) in the

absence of detailed and relevant data. In addition to this, the model only provides single

point estimates of a particular risk. This does not allow for uncertainties to be quantified

although the model does allow for explanations to be included when default values are

changed.

3.5.3 Assessment Standards

In order to determine whether a risk is being posed and to what extent, clear and well-

defined assessment standards need to be used. If the standards are exceeded, it is an

indication that appropriate remedial action is required. SDA (2000) compared their soil

sample data with three different assessment standards. These were:

1. Trigger concentrations of contaminants as specified in the Department of

Environments Interdepartmental Committee on the Redevelopment of

Contaminated Land (ICRCL). These concentrations are set for a number of

different contaminants and vary according to the end uses of the site. If

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contaminant values are below the relevant trigger concentrations, the site is

considered to be uncontaminated. In the case of the Greenside site the nearest

equivalent end use was chosen by SDA (2000) to be as parks, playing fields and

open spaces. The trigger concentration for lead for this particular end use is set at

2000 mg/kg (Department of the Environment, 1983 from SDA, 2000).

2. Greater London Council Guidelines (GLC Guidelines) for the Assessment of

Contaminated Land (SDA, 2000).

3. Dutch Guidelines (Moen, 1994).

No UK assessment standards exist for groundwater in the UK and accordingly the SDA(2000) report, in keeping with the operating practice of the EA, adopted the Dutch

Guidelines.

3.5.4 Principal Findings and Recommendations

The findings of soil lead content by SDA (2000) reflected that of other Lancaster

University dissertation students, namely that those from the tailings dams were lower

than surface samples collected elsewhere on the site. SDA (2000) felt that there was no

adverse levels of contamination in surface waters but acknowledged there to be elevated

levels of metals in groundwater within the tailings dams. Findings relating to the lead

content of soil, surface water and groundwater are referred to in some detail in section 6

of this report.

The principal risk posed by the mine site was found to be a further collapse of the

unstable TD2 and the resultant contamination of surrounding water systems from the

high lead content of the dam. The remedial measures recommended by SDA (2000) to

the LDNP Authority address this principal risk. The structural engineering assessment

which was carried out identified other structures on the site, such as walls, which also

require remedial work. Funding has been secured for the necessary remedial work from

the Environment Agency and the Department of Environment, Transport and the Regions

(Guy Weller, LDNP Authority, pers. comm., 2000).

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4.0 EXPERIMENTAL METHODS

This section of the report provides an overview of the methods of the experiments that

were adopted as part of this investigation. In order to try to quantify the amount of

contaminant that would enter the water system if either tailings dam were to fail, it was

necessary to gain an understanding of the metal composition of each dam. X-ray

fluorescence spectrometry (XRF) was adopted to determine the lead content of soil

samples obtained from the tailings dams. The pH, organic matter content and percentage

of particles

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15cm2 of turf was first removed from each sampling location before pits were dug to

obtain the soil samples. Care was taken to ensure that the root system remained intact

with the turf. The samples were placed in individual and referenced sample bags for later

use in determining the lead content of the grass at each sampling location.

Pits were dug with a shovel at each of the six locations on the tailings dams to a

maximum depth of 0.58m. It was not possible to dig a pit to collect soil samples at the

control location due to the amount of large rock present. Instead, an exposed location

was identified near the footpath (see Figure 8 below).

Figure 8: a photo of the control site taken at NGR NY 363173 looking South.

Soil samples were taken from each distinct soil horizon within each pit and from the

control site. Figures 9 and 10 overleaf are photos showing pit D and pit G respectively.

Figure 11 is a grass and soil sample chart indicating the reference number for each

sample. The depth in cm at which the soil samples were obtained is also provided

together with a brief description of each.

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Figure 9: a photo of pit D taken at NGR NY 366175.

Figure 10 a photo of pit G taken at NGR NY 364175.

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Depth Contro TD1 TD2from Site/Pit Pit B Pit C Pit D Pit E Pit F Pit G

Surfac A/G B/G C/G D/G E/G F/G G/G LEGEN1 A/S1 B/S1 C/S1 D/S1 E/S1 F/S1 G/S1 Root2 Zon3 Dark4 D/S2 soil5 Brown

6 D/S3 Light7 A/S2 G/S2 soil8 C/S2 F/S2 Grey/brow9 E/S2 soil

10 B/S2 E/S3 Grey11 F/S3 Coarse12 B/S3 C/S3 E/S4 grain13 C/S4 E/S5 Coarse14 F/S4 G/S3 Coarse15 G/S4 some16 length17 A/S3 fragment18 F/S5 presen19 Fine20 Cream21 coloured22 C/S5 Brown23 E/S6 coloured24 Grey25 D/S4 G/S5 clay26 Cream clay27 coarse28 E/S7 F/S6 Ferrous29 colou3031 A/S4 B/S432333435 G/S63637 D/S5 G/S738 B/S5 F/S73940 G/S84142 B/S6 D/S643 C/S6444546

4748 F/S849505152 D/S753545556 D/S85758

Figure 11: A soil and grass sample chart to indicate the depth from the surface in cm

at which the samples were taken and a brief description of each.

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Samples were removed using a small plastic spade and collected in sample bags. The

depth from the surface at which each sample was obtained was determined by use of a

metre rule. Each bag was referenced according to the date of collection, sample

reference and depth in cm. The number of soil samples obtained ranged from four to

eight samples per pit.

Due to time constraints the soil and grass samples were collected from the site on two

separate days but within the same week. The control samples and those from TD1 were

collected on 13 June 2000. The samples from TD2 were obtained on 16 June 2000.

All samples were transported back to Lancaster on the day of collection. Each sample of

soil was removed from the collection bag and placed on a lined tray that wasappropriately labelled. Each sample was air dried for three days to remove excess

moisture. Due to the high moisture content of the clay samples, they were oven dried

overnight at 40C to speed up the drying process.

The samples were stored in a dark (except when samples were added/removed) cold

room at 4C until required for analysis. This measure was taken to help preserve the

integrity of each sample. The samples were stored up to a maximum of six weeks before

analysis.

4.2 Sub-sampling Procedure

All the experiments that were carried out on the soil samples required far less material

than was actually collected. In order to obtain a representative sub-sample a method

known as coning and quartering was adopted.

Firstly, the entire sample was shaken vigorously in the sample bag to avoid any bias due

to settling effects. The sample was poured onto a clean sheet of glass in the form of a

cone. Using a wide, flat spatula, the cone was pressed down until the sample was a flat,

circular shape. The sample was then carefully divided into four equal quarters using a

spatula. Two quarters lying opposite to each other were placed to one side for use in

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further experiments. The remaining two quarters on the sheet of glass were retained for

further coning and quartering. This procedure was repeated until the amount of material

remaining was appropriate to the particular experiment being carried out (Radojevi,

1999).

4.3 Laboratory Water

When water was required in the preparation or analysis of samples, Milli-Q water was

used. This measure was taken in order to avoid contamination of the samples from tap

water.

4.4 Glassware

All the glassware used was acid washed in 10% Nitric Acid for a minimum of one and a

half hours except the crucibles. These were instead washed using concentrated washing-

up liquid, rinsed, oven dried at 100C overnight and kept in a drying cabinet until

required.

4.5 Sample Handling

Polyethylene gloves were worn at all times when handling the grass and soil samples for

two main reasons. Firstly, in order to avoid contamination or interference of the samples

and secondly to avoid ingestion of soil.

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4.6 Lead Content in Grass

Firstly, soil was rinsed off the grass samples prior to the analysis of the latter. This

procedure was carried out to ensure that only the lead content of the grass and not the soil

was determined. The grass samples were dried overnight in an oven at 30C. Each

sample was digested in nitric acid and filtered prior to the lead content of each being

analysed by atomic absorption spectroscopy (AAS). A 280 AAS Perkin-Elmer was used

in this experiment. The slit width was set to 0.7nm and the wavelength of the lamp to

282.3h.

Absorption readings were first obtained by AAS of six standard calibration solutions.

The data were plotted against the known lead concentration of each solution to form acalibration curve. The lead concentration in each of the grass sample solutions was

obtained from the calibration curve using the absorbency reading obtained by AAS.

The lead concentration of each solution was first multiplied by the volume of that

solution. This value was then divided by the dry mass of the grass to give the lead

content in mg/kg for each grass sample. Detailed information relating to the above

method and this calculation are provided in Appendix B.

4.7 Sheep Ingestion Calculation

The LDNP Authority was advised in the SDA (2000) report that sheep should be

discouraged from grazing on the grass covering TD1 and TD2. The advice was based on

the high levels of lead that had been determined by SDA (2000) to be present in surface

soil of the surrounding area. Neither herbage tests nor sheep grazing ingestion

calculations such as that designed by Hope (1995) had been carried out by SDA.

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The LDNP Authority did not consider the root system of the turf to be in contact with the

contaminated tailings material. Consequently, they felt that there was no significant

contamination risk posed to the sheep grazing on the tailings dams. Furthermore, the

LDNP Authority felt that grazing stimulated the root growth of the turf thereby assisting

the stabilisation of the tailings dams (Guy Weller, LDNP Authority, pers. comm., 2000).

The lead body burden on a sheep as a result of lead ingestion due to grazing was

determined from Hopes (1995) ingestion calculation. The lead body burden on a sheep

from lead ingestion due to grazing on the control site, TD1 or TD2 from 0 to 365 days a

year was calculated. Data derived from the analysis of the grass and soil samples was

incorporated into the calculation. Lead content in water from the site was obtained from

SDA (2000) data.

A full breakdown of Hopes (1995) calculation and the data that was incorporated into it

is provided in Appendix C. It was anticipated that the findings from this calculation

would lend weight to either SDAs (2000) argument or that of the LDNP Authority.

4.8 Lead Content in Soil

SDA (2000) determined the thickness of the tailings for TD1 and TD2 from results of

dynamic probe tests. The tailings material of TD1 was found to have a thickness ranging

between 5.8m and 14.1m. A tailings thickness of between 3.2m and 7.4m was found for

TD2. Soil samples obtained for analysis during this investigation were from a maximum

depth below the surface of 0.58m. Consequently, approximately 4-10% and 8-18% of

the tailings thickness of TD1 and TD2 respectively, was investigated. No analysis was

carried out on the foundations of either tailings dam, which for TD1 is an old spoil heap.

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The content of lead and other geological minors was determined by XRF for each soil

sample collected from the control site, pit D and pit G. Additional samples (B/S2, C/S2,

E/S3 and F/S2) were tested from what was believed to be the organic layer of the other

four sample pits.

3g of each sample was ground by hand until all the particles could pass through a 100m

sieve. Compressed powdered briquettes were made from each ground sample for

analysis by XRF. A PW 1400 Philips Spectrometer was used to analyse the samples. A

more detailed breakdown of the method that has been outlined above is provided in

Appendix D.

4.9 Organic Matter Content in Soil

The organic matter content was established for all of the soil samples. 2g of each sample

was placed in a crucible and put in a furnace for 2 hours at 500C. The weight of organic

matter in each sample was obtained by subtracting the post-furnace weight of the sample

and crucible from the pre-furnace weight. The weight of organic matter was divided by

the pre-furnace weight of the sample. This value was multiplied by one hundred to

provide the percentage of organic matter in the sample. A more detailed description of

the method followed is provided in Appendix E.

4.10 Soil pH

The pH value was obtained for all soil samples collected from the control site, pit D and

pit G. Additional samples (B/S2, C/S2, E/S3 and F/S2) were tested from what was

believed to be the organic layer of the remaining four sample pits. 10g of each dried soil

sample was made up into a soil suspension and the pH measured using a PHM220 pH

Meter known as a MeterLab. Prior to the testing, the pH meter was calibrated using pH

4.0 and 7.0 buffers. A more detailed description of the method followed is provided in

Appendix F. The data are presented in Table 5 of section 5.0 of this report.

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4.11 Grain Size Analysis

A grain size analysis was carried out on all soil samples collected from the control site,

pit D and pit G. Additional samples (B/S2, C/S2, E/S3 and F/S2) were analysed from

what was believed to be the organic layer of the remaining four sample pits.

The distribution of particles ranging between 1-200m was determined using a

Micrometrics Sedigraph 5100. Wet sieving was carried out on those particles between

201-2000m in size.

The dry mass of the sample

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5.0 EXPERIMENTAL FINDINGS

This chapter of the report provides a summary of the results from experiments that were

carried out on grass and soil samples as detailed in the previous chapter.

5.1 Grass Samples

The mean absorbency reading obtained for each of the standard calibration solutions is

shown in Table 2 below. The standard deviation of each absorbency reading was

calculated and is also included in Table 2.

Table 2: Absorbency readings and standard deviations for the standard Pb calibration

solutions.

Standard Pbconcentration

gcm -3

Meanabsorbency

readings

Standarddeviation of

absorbency

readings

0 0.000 0

5 0.060 0.0006

10 0.107 0

15 0.158 0.001

20 0.204 0.0012

30 0.298 0.0015

AAS derived absorbency readings of the six standard calibration solutions were plotted

against their known lead concentrations to form a calibration curve (see Figure 12). The

gradient of the curve was calculated to be 0.0102.

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y = 0.0102x

R2= 0.9966

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0 5 10 15 20 25 30 35

Lead concentration (ug/cm3)

Absorbance

Fi

gure 12: A Calibration Curve of Absorbance Against Lead Concentration

It was noted that, with reference to the Beer-Lambert Law, the calibration curve plotted

indicated a good linear relationship between absorbance and concentration. The R2 value

was calculated to be 0.9966. Possible causes for the position of plots slightly away from

the line of best fit are referred to in Section 6 of this report.

Some of the sample solutions were diluted to 1:2 or 1:10 depending on the reading

obtained from their initial AAS testing. The dilution factor was taken into account

during the calculation of the lead concentration for each grass sample solution.

The mass of lead per unit mass (dry weight) of grass is shown in Table 3 for each of the

grass samples tested together with the blank. The latter provided a value of zero as

expected. The range of lead contents in the grass samples was 7341mg/kg with the

control site sample providing the lowest value of 299mg/kg and the highest being

7640mg/kg from sample BG of TD1. Full details of the data obtained from this

experiment are provided in Appendix B.

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There is a significant difference between the lead content of 299.1mg/kg from the grass

sample obtained from the control site and the average lead content in the grass samples

from TD1 of 3,147.0mg/kg and of 3,035.8mg/kg from the TD2 grass samples.

Table 3: Content of lead in mg per 1kg of dry weight grass for each grass sample and the

blank.

SampleNos

Content of lead in mg per1kg of dry weight grass

A/G 299.1

B/G 572.0

C/G 7,640.2

D/G 1,228.8

E/G 1,385.9

F/G 2,444.1

G/G 5,277.3

Blank 0.0

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5.2 Sheep Grazing

A graph (see Figure 13) was drawn to indicate how the lead body burden on a sheep

varied with the number of days a year it grazed at a particular location. In addition to

this, the lead limit range of 0.05-0.2 mg/kg proposed by the European Commission for

sheep and the mean lead content 0.03 mg/kg for lamb cuts (see Section 2.3 of this report)

has also been displayed in Figure 13. The data obtained from the calculations have been

included in Appendix C.

Figure13: A graph to indicate the range of lead contaminant body burden on a sheepgrazing from 0 to 365 days a year on either the control site, TD1 or TD2. Lead content

limits for sheep and lamb cuts are displayed.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 100 200 300 400

Number of days in a year that sheep graze on

the control site, TD1 or TD2

Leadcontam

inantbodyburdeninsheepfrom

lead

ingested,mg/kg

Control Site

TD1

TD2

Linear (Upper

Pb limit forsheep)Linear (Lower

Pb limit for

sheep)Linear (Max Pb

conc for lamb

cuts)

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5.3 Soil Samples

5.3.1 Lead Content by XRF

Each pit contained distinct horizons, each differing in grain size, consistency and colour.

It was noted that except for the root zone samples, there was no microbial activity in any

of the samples.

The XRF derived lead content values in mg/kg for each sample briquette tested is

provided in Table 4 overleaf. The high lead content that was present in the soil samples

was thought to have interfered with the arsenic readings from the XRF analysis and

consequently the latter have been ignored. Appendix D contains the full set of data

relating to the content of the geological minors in each sample.

The calibration range for lead was given as 4 to 58mg/kg. As can be seen from Table 4,

all the lead values obtained are significantly beyond this range and have been acquired

from the extrapolation of the calibration values. Consequently, the values may not be

exact but provide a good indication of the lead levels present at the site.

The standard deviation for the quality control value was zero for lead. A range of

28,887mg/kg exists for the lead contents found in the soil samples. The values obtained

from the control site samples (Sample numbers A/S1 to A/S4) are significantly lower

than those taken from the two tailings dams.

The lead content values of the control site samples ranged from 62mg/kg to 675mg/kg

with an average of 340mg/kg. In contrast, the lead content of TD1 soil samples ranged

from 1,993mg/kg to 28,949mg/kg with an average of 13,115mg/kg. The lead content of

TD2 soil samples was also higher than those found in the control site samples. The lead

content values of the former ranged from 1,844mg/kg to 11,950mg/kg with an average

value of 6,025mg/kg.

The lead content in the root soil sample obtained from the control site is 509mg/kg

compared to an average content of 4,152mg/kg from the root soil samples of TD1 and

6,534mg/kg from those obtained from TD2.

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Table 4: XRF derived lead content values in mg/kg of soil samples from the control site,

TD1 and TD2.

Pb

mg/kg

QCE* 7.5Mean QCA** 9.0

QCD*** -1.5

Standard Deviation 0

A/S1 675

A/S2 509

A/S3 115

A/S4 62

B/S2 4,362

C/S2 3,925

D/S1 4,106

D/S2 4,169

D/S3 1,993

D/S4 28,949

D/S5 13,117

D/S6 18,602

D/S7 21,115

D/S8 12,865

E/S3 2,368

F/S2 5,283

G/S1 6,813

G/S2 11,950

G/S3 4,473

G/S4 5,026

G/S5 3,032G/S6 10,355

G/S7 4,709

G/S8 1,844

All the lead content values were found to be outside of the calibration range.

*QCE: Quality control value that was expected to be obtained;

**QCA: Quality control value that was actually obtained;

***QCD: Quality control difference = QCE QCA;

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5.3.2 Soil pH, Organic Matter & Grain Size Analysis

The soil pH, the percentage of organic matter in each sample and the percentage of grain

particles in each sample which was less than 180m in size are detailed in Table 5

overleaf. The lead content for the grass and soil samples which were obtained by AAS

and XRF techniques respectively are also included in Table 5.

The mean percentage of organic material did not significantly vary between pit locations.

The mean percentage contained in the pit A (control site) samples was 8% compared to

10% in the pit D samples and 13% in the pit G samples. However more variation existed

when comparing the range of values present within pit A to that in pits D and G. The

range of organic matter percentages within pit A was 10 compared to that of 41 for pit Dand 38 for pit G. The data that were obtained at the various stages of this procedure are

displayed in Appendix E.

The pH values shown in Table 5 vary from 4.15 to 6.84, a range of 2.69. The pH values

do not appear to correlate with the lead content of the samples nor any other factor which

was considered during this investigation. However, the samples closer to the surface in

both tailings dams are more acidic than those collected from greater depth. This pattern

is not reflected in the control site pH values.

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Table 5: Lead content, pH, percentages of organic matter and grain size

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The percentage of each soil sample that was in a particular pre-determined particle size

category, ranging from 2000m, is contained in Appendix G. This data

has been presented diagrammatically in Figure 14. Only the cumulative mass percent for

soil samples taken from the soil sample immediately below the root zone of each sample

site have been included in the graph. Particles 2000m.

The data that were obtained at the various stages of the grain size analysis are displayed

in Appendix G.

Figure 14: A graph to show the cumulative mass percent for each soil sample.

0%

10%

20%

30%

40%

50%

60%

70%80%

90%

100%

A/S2 B/S2 C/S2 D/S2 E/S3 F/S2 G/S2

Soil Sample Number

Grainsizeas%o

ftotalsam

ple

>2000um710-2000um

600-710um

500-600um

212-500um

180-212um

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6.0 DISCUSSION

This section of the report interprets and discusses the findings of this investigation.

Whilst the range of risks that the site poses is outlined, attention has primarily been paid

to the risk of lead contamination. The outcome of the human health assessment carried

out by SDA (2000) determined that there was no contamination risk posed to visitors to

the site from soil ingestion or inhalation. Further information relating to SDAs (2000)

findings has been provided in Section 3 of this report.

The lead content and structural stability of the tailings dams are discussed in this section

of the report together with the contamination risk posed to sheep grazing on the site. The

findings and conclusions of investigations carried out by SDA (2000), the EA (2000) and

other Lancaster University dissertation students into other aspects of lead contamination

are referred to. The section concludes with the identification of sources of uncertainty

and error associated with this investigation. These have been quantified where possible.

6.1 General Risks

There exist a wide variety of risks associated with the Greenside site. Those risks

identified by SDA (2000), EA (2000) and this investigation include:

i) structural failure of the tailings dams;

ii) soil contamination;

iii) sediment contamination;

iv) groundwater contamination;

v) surface water contamination of Swart Beck, Glenridding Beck and Lake Ullswater;

vi) detrimental affect on the health of sheep grazing at the site and in turn the human

food chain;

vii) detrimental affect on the health of the general public;

viii) structural instability of some of the walls on the site;

ix) instability of mine entries and underground workings.

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6.2 The Tailings Dams

6.2.1 Geotechnical Stability

The geotechnical stability of both TD1 and TD2 was assessed by SDA (2000) and the

key influence on the slope stability of each was found to be groundwater. No remedial

work was deemed necessary for TD1 providing there was no deterioration in its current

condition. In contrast, investigations carried out on TD2, found it to be structurally

unstable and possessing a high metal content, particularly so for lead.

Lead levels within the tailings dams were found by SDA (2000) to be above ICRCL

threshold levels and Dutch intervention levels. (Section 2 of this report briefly refers to

both of these assessment standards). Other heavy metals that are known to be associatedwith galena such as cadmium, copper and zinc were also found to be above these two

levels but to a lesser extent in comparison to lead.

In the event of TD2 failing, a large amount of particulate with high metal content would

be introduced into the water system and ultimately Lake Ullswater. This contamination

risk was deemed by both SDA (2000) and the EA (2000) to represent the principal risk

posed by the site on the surrounding environment. Remediation measures that are

required to address this risk focus on the need to stabilise and cover the tailings dams.

More information relating to these measures are provided in section 7 of this report.

6.2.2 Physical Characteristics

SDA (2000) determined that the outer embankments slopes of the tailings dams consist

of loose to medium dense, fine to medium sand. However the inner core of each

comprise of layers of soft sandy silt and silty clay. During this investigation, discrete

horizontal layers were found to exist in the sample pits from TD1 and TD2 (see Figures 9

and 10 of section 4). SDA (2000) suggest that this could be due to the intermittent

intrusion of ponded water into the sandy beach deposits that the tailings deposition

process is believed to have yielded.

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All the soil samples obtained from the tailings dams pits contained particles no larger

than 1cm in size. This is in stark contrast to the boulder-sized fragments that lie

underneath the tailings material of TD1. These larger fragments of waste material are the

result of mining activity that occurred decades earlier, at a time of lower processing

efficiency.

Soil particles from TD1 and TD2 samples are angular suggesting they have undergone

little erosion and confirming they are the product of mining activity. The predominantly

small particle size of the samples could be a result of the crushing that would have taken

place during the processing of the lead ore.

6.2.3Lead Content

Levels of lead and other contaminants from TD1 and TD2 soil samples were lower than

those found in surface soil and sediment samples which had been collected elsewhere on

the site (Kember, 2000; SDA, 2000).

The lead content of the control site soil samples was found to be significantly lower than

those obtained from the tailings dams. In an effort to better understand the variation in

lead content between and within the sample sites, possible influencing factors such as

soil pH and organic matter were measured.

Figure 15 consists of three graphs containing data obtained from (A) pit A of the control

site, (B) pit D of TD1 and (C) pit G of TD2. The lead content of the soil samples is

compared with the organic matter content expressed as a percentage, the pH value and

the percentage of the sample that contains particles

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The uppermost three soil samples from pit D have lower lead contents than the soil

samples taken from greater depth. However, there is a significant variation of lead

content within these two sub-groups. Similar lead content values exist between the soil

samples obtained from immediately below the root zone soil in each of the sample sites

of TD1 (B/S2, C/S2, D/S2). No relationship between depth and lead content appears to

exist in pit G.

6.2.4 Risk Probability Analysis

It is likely that with increasingly efficient processing methods, the lead content of waste

from the mine reduced over time. Therefore the tailings material analysed during thisinvestigation could contain less lead than waste material at greater depth in the dams or

located elsewhere on the site. Accordingly, the contamination risk associated with the

introduction of particulate into the water system following a failure of TD2 may be

higher than first anticipated.

Whilst initially it may appear that the material analysed presents the least contamination

risk of the entire dam, this need not be the case. This investigation did not incorporate a

risk probability analysis. If this had been considered then it may have found that

although of a lower lead content than material beneath it, the top of the tailings dam may

be the least stable part of the dam. The probability of the collapse of this part of the dam

may be significantly higher when compared to that of the material below it. The

cumulative effect of a number of small slippages of the tailings material over a period of

time may be equal to or in excess of a major one-off slippage of older material that has a

higher lead content. Further investigation is required before this type of probabilityanalysis can be carried out.

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6.2.5 Factors Influencing Lead Bioavailability

It is known that the bioavailability of lead can be influenced by soil parameters such as

the soils organic matter content, pH and particle size. A correlation was expected

between these factors and the lead content values of the soil samples which were

analysed.

It was envisaged that the soil samples immediately below the root zone would contain the

highest percentage of organic matter due to the texture and colour of these samples.

Furthermore, that this would promote the binding of lead to the organic matter and a

positive correlation to exist between the two. However, a positive correlation of this

nature was not found to exist. The organic matter content was the highest in the actual

root zone samples within some of the sample pits. Overall there is a significant decreasein the percentage of organic matter content of each sample pit with increased depth from

the surface. However, this was expected given the presence of the turf and its associated

natural decomposition processes.

The soil pH values appear to be inversely related to the depth at which the sample was

taken. The greater the depth, the lower the pH value. pH values obtained within the first

6cm of soil from TD2 are lower than those from comparable sample depths in TD1 or the

control site. The soil pH values do not correlate with the lead content values obtained in

each of the samples.

No correlation was found between the lead content of a sample and the percentage of

particles

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6.2.6 Groundwater Contamination

Groundwater samples were obtained from piezometers in probe holes on both TD1 and

TD2 by SDA (2000). Both sets of samples contained significantly higher levels of heavy

metals than samples analysed from the surface waters of the tailings dams and pipe

discharges from the dams.

6.3 Contamination Risk to Sheep

There is a two-fold risk posed by grass containing elevated levels of lead such as that

which was analysed on the two tailings dams. Firstly, there is a direct risk to the health

of sheep grazing on the grass. High lead levels in sheep will potentially be passed on to

their unborn young. Thereby, giving rise to a secondary risk to human health from the

consumption of lamb containing elevated levels of lead.

6.3.1 Lead Content of Grass Samples

In common with the soil samples, the lead content of the control site grass samples was

found to be significantly lower than those obtained from the tailings dams. The lead

content of the control site grass sample was calculated to be 299mg/kg compared to a

mean lead content of 3147mg/kg from the TD1 grass samples and 3036mg/kg for the

TD2 samples.

Whilst the lead content of the grass samples obtained from TD1 is highly variable

between the different sample sites. The values obtained from the TD2 samples decreased

with distance from the slippage area. This reflected the negative correlation between

lead content and distance exhibited by the TD2 root zone soil samples.

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All the grass samples have a significantly lower lead content than the soil in which their

root system is in contact with except for the grass sample obtained from pit B. The lead

content of grass was found to increase with increasing lead content in the soil

immediately below the root zone. Figure 16 is of a graph indicating this relationship.

Figure16: A bar chart to compare the lead content of each grass sample and that of the

soil immediately below the root zone.

Jopony and Young (1993) also found that the uptake of lead by plants was poorly

correlated with both pH and the total lead content of the soil. They proposed that the

lead content of the soil solution in the root zone provided a better index of lead

availability. Total lead uptake by plants was found by them to be of the same order of

magnitude as the total lead content of the soil solution in the root zone.

The variation between lead content of grass and root zone soil samples from the samepits could be due to the influence of a number of soil parameters as well as the physio-

chemical form of the lead itself. Lead is known to bind to iron and manganese oxides,

thereby reducing its bioavailability to plants. The content of these oxides in the soil

samples has not been analysed and consequently it has not been possible to determine

whether they are an influencing factor on the lead content of the soil and grass samples.

0

2000

4000

6000

8000

10000

12000

14000

A B C D E F G

Pit Reference

Pb

Content(mg/kg)

Grass Sample

Sub Root Zone

Sample

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6.3.2 Lead Ingestion Calculation

The lead body burden on a sheep as a result of lead ingestion due to grazing was

determined from Hopes (1995) ingestion calculation. It was assumed that the body

burden of a sheep would be the same as that for its young. The findings of this

investigation support the SDA (2000) reports recommendation that sheep should not

graze on the tailings dams. It is estimated that after just several days there is a significant

risk of contamination to sheep from grazing on the site.

Harrison and Laxen (1981) estimate that 99% of all lead ingested is excreted in the

faeces. Consequently, it may be thought that there would be little impact on the food

chain from the ingestion of lead by sheep. However, even with the inclusion of this large

absorption inefficiency, the contaminant body burdens obtained from Hopes (1995)

ingestion calculation, would suggest otherwise.

Only those lead body burden values calculated for the control site grazing were found to

be either below or within the lead limit range proposed by the European Commission

Regulation (lll/5125/95 Rev.3) (ECR) for sheep. It was calculated that the lead body

burden of a sheep would be in excess of the mean lead content set by the Food Standards

Agency for lamb cuts of 0.03 mg/kg if it grazed in excess of 100 days at the control site.

The mean lead content set for lamb cuts was exceeded within a few days for sheep

grazing on either TD1 or TD2. Lead body burden values were very similar from both

sites and exceeded the upper ECR lead limit for sheep after approximately 60 days of

grazing. However TD1 derived values were consistently greater by a matter of 0.01-0.04

mg/kg compared to TD2 derived values.

It is possible that during the course of a year the lead body burden of sheep grazing on

contaminated grass will fluctuate. Mitchell and Reith (1966) found that both the uptake

of lead by plant roots and translocation to the shoots varies seasonally. The collection

and analysis of the grass samples was carried out in June 2000. As June falls in the

period of minimum lead uptake, it is possible that the ECR value for sheep would be

exceeded during the winter months on the control site as well as the tailings dams. This

in turn would lead to the recommendation that sheep are prohibited from grazing

anywhere on the site and not just the tailings dams.

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The application of Hopes (1995) ingestion calculation provides only a very rough

estimate of the lead body burden of sheep through soil and grass ingestion. It does not

accurately quantify lead absorption by sheep nor what proportion is passed to its unborn

young. This quantification could however be achieved by analysing either blood samples

whilst the animal is alive or muscle samples when it is dead. The latter is clearly not

ideal for inclusion in a regular monitoring program given its destructive nature.

6.4 Surface Water Contamination

Maxwell (2000) compared the lead concentrations in water samples obtained throughout

the mine site down to Lake Ullswater, against drinking water standards set by theEuropean Commission (EC) and UK Regulations. The lead concentrations in

Glenridding Beck (downstream of the mine site) and Lake Ullswater were found to be

either approaching or exceeding the EC and UK allowable maximums. However,

Maxwell (2000) suggested that the current concentration levels of lead in the water,

whilst elevated, posed no significant threat to humans, animals or fish.

6.5 Sediment Contamination

Sediments in Glenridding Beck were found by Kember (2000) to increase in lead content

from 1,019mg/kg upstream of the confluence with Swart Beck, to 23,612mg/kg

downstream of the confluence. However, the lead content of sediments from Lake

Ullswater was found to be 6,412mg/kg. Kember (2000) determined that the metal

content of sediment samples taken from above the mine site in Swart Beck and

Glenridding Beck through to Lake Ullswater, decreased with increased distance from the

mine site.

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6.6 Water Quality

The contamination of Lake Ullswater is of particular concern with regard to drinking

water quality. It is used as a reserve by North West Water for the Greater Manchester

area (Guy Weller, LDNP Authority, pers. comm., 2000). Accordingly, the water quality

of Swart Beck and Glenridding Beck, as tributaries to Lake Ullswater, is also of

importance.

As a popular location for leisure activity such as sailing and diving, the water quality of

Lake Ullswater is also of significance to the local economy. In addition to this, the lake

supports populations of both salmon and the Schelly. The latter is protected under the

1981 Wildlife and Countryside Act and Lake Ullswater is one of the few sites in the

United Kingdom in which it survives. The lead EQS of 2ug/L for salmonid watercourses

such as Glenridding Beck and Lake Ullswater was found to be exceeded in the water

samples analysed by EA ( 2000).

The EA (2000) identified in their report the increasingly eutrophic nature of Lake

Ullswater. Their concern is that in conjunction with increasing eutrophication there is a

lowering of water pH values. The latter results in an increased risk of remobilisation of

heavy metals from the lake sediments. The EA (2000) state that the current secondary

release of selenium from sediments within Lake Ullswater, is a precursor to the release of

other metals such as lead.

During the majority of Greenside Mines long history, waste material was discharged

directly into Glenridding Beck. It is likely, as Kember (2000) states, that the ultimate

sink for sediments contaminated by such waste is Lake Ullswater. Consequently the

secondary release of metals from lake sediments poses a potentially significant

contamination threat to the water quality of the lake.

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6.7 Instability Risk from Mine Entries and Underground Workings

A detailed mineworkings risk assessment has not been carried out at the site although the

risk to the general public is considered to be low. The large subsidence features on the

flanks of Greenside represent a potential hazard to the public due to their depth (the

deepest being an estimated 80m deep) and near vertical sides. Remedial works such as

infilling are not considered feasible due to the size of these features. However, it is

recommended that they are adequately fenced to prevent unauthorised access. The risk

of mining induced ground settlements was considered remote SDA (2000).

6.8 Experimental Uncertainty and Errors

Whilst steps were taken throughout this investigation to protect the integrity of the

samples, it is inevitable that errors were introduced. Although it has been possible to

identify a number of sources of errors, it has proved more difficult to quantify them.

Sample contamination could potentially have occurred at any stage of the investigation.

The spade and plastic trowel that were used to respectively dig the pits and collect the

soil samples, may have provided sources of contamination. The same could be said for

the sample storage bags, the steel equipment and substances used during the analysis of

soil and grass samples. However, metal contamination from these sources is likely to be

minimal. For instance, the AnalaR nitric acid that was used during the grass sample

analysis was predicted to have a lead residue on ignition of 5 x 10-6%.

The calibration of the XRF machine was carried out using a basaltic rock standard. This

was considered to be the nearest comparison to the material being analysed but by not

being an exact match to it, provides a source of error. In addition to this, the soil lead

content values were all significantly beyond the maximum calibration value of 58mg/kg.

The values were all obtained from the extrapolation of the calibration values and

therefore there is a degree of uncertainty concerning the accuracy of these results.

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The root zone soil samples were found to have high lead contents. Therefore, it is likely

that any soil that was not washed off the grass samples prior to analysis would have

affected the grass lead content values. It is not however possible to quantify this error.

Instead, steps could be taken to reduce this source of contamination by adopting a more

rigorous rinsing method. Alternatively, only that part of the plant that is above ground,

an